Not to diminish your work, but your previous one was better... Where does the light on the hood of the XRR come from? If it's a stationary one in front of the car, why does it shine only on the car and nowhere else? Nice touch on the spray under the car, but especially under cornering it would cover the whole side of the car, not stay neatly under it... You also would see rain (illuminated by the headlights) against the dark grass farther ahead than you showed... And lastly if the car behind has his lights on, why can't we see them through the windows even if they are tinted (which nobody in his right mind would do in a race going into the dark)...
Various brush work. I use a Wacom tablet which is great for doing things like that by hand, just use the brush tool and the smudge tool for the details. Then play around with extra layers and different opacity settings.
And thanks JJ72 for explaining the various reasons for the details. You said it all in far less words than I'd have been able to.